A new insider survey of 58 legal experts conducted after the oral arguments concluded found that most predict that the court will strike down the so-called individual mandate, a central provision within the law requiring that every American purchase a government-approved form of health insurance. The same expert survey was conducted before the hearings began, which found the opposite: Most thought the law would be upheld.

The survey was paid for the American Action Forum, a right-leaning organization and Center Forward, a centrist group, both based in Washington, D.C. It was conducted by Purple Insights, a bipartisan consulting firm. The pollsters received input from former clerks who have worked for justices on both sides of the ideological spectrum…..

Using a scale from 0 to 100, the pollsters asked the 38 former clerks of current Supreme Court justices and 18 attorneys who have argued before the court to rate the probability that the individual mandate provision would be declared unconstitutional. The insiders provided an average rating of 57 percent, a significant jump from the pre-hearing survey, when the average was just 35 percent.

The full survey results, including predictions on severability and the Medicaid case, can be found here.

As I pointed out in this post, even the average pre-argument estimate of a 35% chance of victory for the plaintiffs suggests that the many pro-mandate pundits who claimed the case was based on extremist thinking and a slam dunk for the government were overoptimistic. A case with a 35% chance of getting five votes in the Supreme Court is likely to be well within the legal mainstream.

FULL DISCLOSURE: I was in fact one of the participants in both polls. I am the person whom the survey report quotes as commenting that “[t]he case largely depends on which way Kennedy and to a lesser extent Roberts go. Before oral argument, I thought the plaintiffs had a 35% chance. The argument led me to up that estimate to 50%.” Readers will have to decide for themselves whether the very close coincidence between my estimates and the average of the other experts shows that I make good predictions or that I’m a conformist.

I am neither a former Supreme Court clerk nor an attorney who has argued before the Court. However, it’s possible that the authors of the survey counted me in the latter category because I have written multiple amicus briefs in Supreme Court cases, including one cited by the majority opinion in Kelo v. City of New London, and one in the individual mandate case itself. If my inclusion was a methodological mistake, it at least had little impact on the overall result, since my predictions in both polls were very close to the average of the other participants.

UPDATE: Various commenters seize on the fact that 18 of the former Supreme Court clerks included in the poll clerked for the four most conservative justices, 9 clerked for Justice Kennedy, and only 11 for the four liberal justices. One can argue that this introduces a conservative skew in the sample of respondents. The survey authors justify this on the grounds that the distribution reflects the overall distribution of the population of former clerks of the nine current justices (the conservative justices have, on average, been on the Court much longer, and so have more former clerks than the liberals).

More importantly, many of the people who clerk for conservative justices are actually liberals. Justice Scalia, for example, is known for hiring at least one liberal clerk every year. There are occasional conservatives and libertarians who clerk for liberal justices. But this is much less common than the reverse, because a very high percentage of graduates of top law schools are left-wing. If the percentage of the 27 who are actually liberal mirrors the real world distribution (which in my experience is about 20-30% liberal clerks for the conservative justices, and under 5% conservative clerks for the liberals), it is likely that the overall conservative-liberal split among the 38 was not far off 50-50. Assuming that 7 of the 27 former clerks for conservative justices are actually liberals, and 1 of the 11 former clerks for liberal justices is actually a conservative, we get an overall 21-17 conservative-liberal ratio.